Chemical mechanical polishing agent kit and chemical mechanical polishing method using the same

ABSTRACT

A chemical mechanical polishing method of the present invention comprises conducting polishing by the use of a chemical mechanical polishing aqueous dispersion (A) containing abrasive grains and then conducting polishing by the use of a chemical mechanical polishing aqueous composition (B) containing at least one organic compound having a heterocyclic ring in addition to the chemical mechanical polishing aqueous dispersion (A). Also A chemical mechanical polishing agent kit of the present invention comprises the chemical mechanical polishing aqueous dispersion (A) and the chemical mechanical polishing aqueous composition (B). The polishing method and the polishing agent kit can prevent an increase of dishing and corrosion of wiring portion to enhance the yield.

FIELD OF THE INVENTION

[0001] The present invention relates to a chemical mechanical polishingagent kit comprising a chemical mechanical polishing aqueous dispersioncontaining abrasive grains and a chemical mechanical polishing aqueouscomposition containing an organic compound having a heterocyclic ring.

BACKGROUND OF THE INVENTION

[0002] With densification of semiconductor devices, wirings formable inthe devices have been made finer recently. Exemplary technologiescapable of attaining much finer wirings include the damascene method.This method comprises steps of filling a trench or the like formed in aninsulating substrate with a wiring material, and then removing an excesswiring material by chemical mechanical polishing to form desired wiring.

[0003] In the conventional chemical mechanical polishing, if wiring isformed by, for example, copper as a wiring material, the copper wiringportion is excessively polished and hence the copper wiring portionsometimes becomes concave. Such concave curve of the wiring is called“dishing” or “erosion”, and this causes the yield loss of semiconductordevices.

[0004] If the polishing time is irreducibly minimized in order to makethe dishing smaller, copper tends to remain on the surface of a barriermetal layer or the insulating substrate. If such a remainder is present,copper sometimes remains on the surface of the insulating substrate evenafter the barrier metal polishing, and this causes great lowering of theyield.

[0005] Moreover, there is another problem that occurrence of scratcheson the wiring or the insulating substrate or occurrence of “corrosion”that is a phenomenon that the copper wiring portion is corroded duringthe polishing has a great influence on the yield.

[0006] In order to inhibit dishing or erosion to thereby enhancesmoothness of the wafer surface or in order to prevent occurrence ofscratches and corrosion, various polishing compositions have beenheretofore proposed.

[0007] For example, Japanese Patent Laid-Open Publication No.163141/1998 discloses that a composition for polishing a copper filmcomprising an abrasive, water and an iron(III) compound is effective inthe inhibition of dishing or scratching. Japanese Patent Laid-OpenPublication No. 160141/2000 discloses that a polishing compositioncomprising an abrasive, α-alanine, hydrogen peroxide and water iseffective in the inhibition of dishing and erosion and that a polishedsurface having excellent smoothness is obtained. Japanese PatentLaid-Open Publication No. 44047/1998 discloses that a chemicalmechanical polishing slurry containing an aqueous medium, an abrasive,an oxidizing agent and an organic acid can reduce imperfection, defectand corrosion of a surface to the minimum level. It also discloses thata surface active agent is effective for the improvement of smoothness ofa wafer surface.

[0008] In the actual chemical mechanical polishing, in order tocompletely remove excess copper present on the barrier metal layer bypolishing, it is necessary to further carry out polishing(over-polishing) even after the barrier metal layer is exposed. In thiscase, there resides a problem that dishing of a wide wiring portion isincreased or corrosion of a copper wiring portion occurs during theover-polishing. Such a problem has caused great lowering of the yield.On this account, a method to completely prevent increase of dishing andoccurrence of corrosion during the over-polishing has been desired. Thatis to say, development of a high-performance polishing method and apolishing agent used for the method has been desired from the viewpointof enhancement of the yield in the polishing process.

OBJECT OF THE INVENTION

[0009] The present invention is intended to solve such problemsassociated with the prior art as described above, and it is an object ofthe present invention to provide a polishing method capable ofpreventing increase of dishing and corrosion of wiring portion duringthe polishing to enhance the yield and a polishing agent used in themethod.

DISCLOSURE OF THE INVENTION

[0010] The present inventor has earnestly studied to solve the aboveproblems and has found that increase of dishing and corrosion of wiringportion during an over-polishing can be prevented by conductingpolishing using a chemical mechanical polishing aqueous dispersion (A)containing abrasive grains and then conducting polishing using achemical mechanical polishing aqueous composition (B) containing atleast one organic compound having a heterocyclic ring in addition to thechemical mechanical polishing aqueous dispersion (A). Based on thefinding, the present invention has been accomplished.

[0011] A chemical mechanical polishing agent kit according to thepresent invention comprises a combination of a chemical mechanicalpolishing aqueous dispersion (A) containing abrasive grains and achemical mechanical polishing aqueous composition (B) which contains atleast one organic compound having a heterocyclic ring, wherein theaqueous composition (B) does not mix with the aqueous dispersion (A).The chemical mechanical polishing aqueous composition (B) preferablyfurther contains a surface active agent.

[0012] It is preferable that (i) the chemical mechanical polishingaqueous composition (B) contains no abrasive grain or contains abrasivegrains in a concentration of not more than ½ the abrasive grainconcentration of the chemical mechanical polishing aqueous dispersion(A), and (ii) the chemical mechanical polishing aqueous composition (B)contains the organic compound having a heterocyclic ring in aconcentration of 0.005 to 3% by weight. It is also preferable that thechemical mechanical polishing aqueous composition (B) further contains asurface active agent in a concentration of 0.005 to 1% by weight.

[0013] It is preferable that the chemical mechanical polishing aqueousdispersion (A) further contains an oxidizing agent, and the chemicalmechanical polishing aqueous composition (B) contains no oxidizing agentor contains an oxidizing agent in a concentration of not more than ½ theoxidizing agent concentration of the chemical mechanical polishingaqueous dispersion (A).

[0014] It is preferable that the chemical mechanical polishing aqueousdispersion (A) contains the abrasive grains in a concentration of 0.01to 5% by weight, an organic compound having a heterocyclic ring in aconcentration of 0.01 to 5% by weight, a surface active agent in aconcentration of 0.01 to 2% by weight and an oxidizing agent in aconcentration of 0.01 to 9% by weight.

[0015] A chemical mechanical polishing method according to the presentinvention is a method for chemical mechanical polishing of a metal layerformed on a surface of a semiconductor substrate, on said surface ametal wiring portion being present, in the production of thesemiconductor substrate comprising the substrate having a trench and ametal material buried in the trench, said metal material forming themetal wiring portion, which comprises:

[0016] polishing the metal layer with feeding a chemical mechanicalpolishing aqueous dispersion (A) containing abrasive grains until alayer different from the metal layer is exposed in a non-wiring areaother than the metal portion, and

[0017] subsequently, polishing the metal layer remaining on thenon-wiring area during the above polishing with feeding a chemicalmechanical polishing aqueous composition (B) containing at least oneorganic compound having a heterocyclic ring in addition to the chemicalmechanical polishing aqueous dispersion (A).

EFFECT OF THE INVENTION

[0018] The chemical mechanical polishing agent kit of the presentinvention and the chemical mechanical polishing method using the kit caninhibit increase of dishing and occurrence of corrosion during theover-polishing and can prevent lowering of the yield.

BRIEF DESCRIPTION OF THE DRAWINGS

[0019]FIG. 1 is a group of views showing exemplary steps of a chemicalmechanical polishing method according to the present invention.

[0020]FIG. 2 is a group of views showing exemplary steps of a chemicalmechanical polishing method according to the present invention.

[0021]FIG. 3 is a graph showing a relationship between a ratio of theover-polishing time to the polishing time until endpoint and dishing.

[0022] Here are symbols in the Figures.

[0023]1: metal material (metal wiring portion)

[0024]2: substrate

[0025]2 a: non-wiring portion

[0026]3 a: barrier metal layer in a trench of the substrate

[0027]3 b: barrier metal layer on the non-wiring area

[0028]4: metal layer

PREFERRED EMBODIMENTS OF THE INVENTION Chemical Mechanical PolishingAgent Kit

[0029] The chemical mechanical polishing agent kit according to theinvention comprises a combination of a chemical mechanical polishingaqueous dispersion (A) containing abrasive grains and a chemicalmechanical polishing aqueous composition (B) which contains at least oneorganic compound having a heterocyclic ring and does not mix with thechemical mechanical polishing aqueous dispersion (A). In this chemicalmechanical polishing agent kit, the chemical mechanical polishingaqueous dispersion (A) and the chemical mechanical polishing aqueouscomposition (B) are not mixed before the kit is used for chemicalmechanical polishing, but when the kit is used for chemical mechanicalpolishing, the chemical mechanical polishing aqueous dispersion (A) isused singly, or is mixed with the chemical mechanical polishing aqueouscomposition (B) to use it. The word “mix” herein denotes that theaqueous dispersion (A) and the aqueous composition (B) are in the mixedstate during the polishing. For example, the aqueous dispersion (A) andthe aqueous composition (B) can be previously mixed and the mixture canbe fed into a polishing apparatus, or the aqueous dispersion (A) and theaqueous composition (B) can be individually fed into a polishingapparatus and they can be mixed in the polishing apparatus or on apolishing pad.

[0030] (A) Chemical Mechanical Polishing Aqueous Dispersion

[0031] The chemical mechanical polishing aqueous dispersion (A) is notspecifically restricted in its composition provided that it is achemical mechanical polishing aqueous dispersion for polishing a metalfilm, but the aqueous dispersion contains abrasive grains and preferablycontains an organic compound having a heterocyclic ring, a surfaceactive agent and an oxidizing agent when needed.

[0032] (Abrasive Grains)

[0033] The abrasive grains for use in the aqueous dispersion (A) arepreferably inorganic particles or organic-inorganic composite particles.Examples of the inorganic particles include fumed silica, fumed aluminaor fumed titania which is synthesized by the reaction of siliconchloride, aluminum chloride or titanium chloride with oxygen andhydrogen in a gas phase through a fumed process; silica synthesized byhydrolysis condensation of metal alkoxide through a sol-gel process; andhigh-purity colloidal silica synthesized by an inorganic colloid processand freed of impurities by purification.

[0034] The organic-inorganic composite particles are not specificallyrestricted in their type, constitution, etc. provided that they areformed in such one united body that the organic particle and theinorganic particle should not be easily separated from each other in thepolishing process. For example, there can be mentioned compositeparticles which are obtained by polycondensing alkoxysilane, aluminumalkoxide or titanium alkoxide in the presence of polymer particles, suchas particles of polystyrene or polymethyl methacrylate, to form apolycondensate, such as polysiloxane, polyaluminoxane or polytitanoxane,on at least surfaces of the polymer particles. In these compositeparticles, the polycondensate thus formed may be directly bonded to afunctional group of the polymer particle or may be bonded through asilane coupling agent or the like.

[0035] The organic-inorganic composite particles may be formed by theuse of the above-mentioned polymer particles and silica particles,alumina particles or titania particles. In this case, the compositeparticles may be formed so that the silica particles or the like arepresent on the surfaces of the polymer particles using thepolycondensate, such as polysiloxane, polyaluminoxane or polytitanoxane,as a binder, or may be formed so that the functional group of the silicaparticle or the like, such as a hydroxyl group, is chemically bonded tothe functional group of the polymer particle.

[0036] Further, composite particles wherein an organic particle and aninorganic particle which are different in the sign of a zeta-potentialare bonded by the electrostatic force in an aqueous dispersion of theseparticles are also employable as the organic-inorganic compositeparticles.

[0037] The zeta-potential of the organic particle is frequently anegative potential over the whole pH region or a wide pH region except aregion of low pH. When the organic particle has a carboxyl group, asulfonic acid group or the like, it tends to have a negativezeta-potential more certainly. When the organic particle has an aminogroup or the like, it sometimes has a positive zeta-potential in aspecific pH region.

[0038] On the other hand, the zeta-potential of the inorganic particleshows a high pH dependence, and the inorganic particle has anisoelectric point at which the zeta-potential is 0, so that the sign ofthe zeta-potential is reversed across that point depending upon pH.

[0039] Accordingly, by mixing specific organic particles with specificinorganic particles in a pH region where the signs of theirzeta-potentials are opposite to each other, the organic particle and theinorganic particle are bonded by the electrostatic force and united toform a composite particle. Even if the signs of the zeta potentials arethe same at the pH during the mixing, the sign of the zeta-potential ofone of those particles, particularly an inorganic particle, can be madeopposite by changing pH, whereby the organic particle and the inorganicparticle can be united.

[0040] On at least surfaces of the composite particles thus united bythe electrostatic force, a polycondensate, such as polysiloxane,polyaluminoxane or polytitanoxane, may be further formed bypolycondensing alkoxysilane, aluminum alkoxide or titanium alkoxide inthe presence of these composite particles.

[0041] The abrasive grains preferably have an average particle diameterof 5 to 1000 nm. The average particle diameter can be determined by theuse a laser scattering diffraction analyser or by observation using atransmission electron microscope. If the average particle diameter isless than 5 nm, a chemical mechanical polishing aqueous dispersionhaving a sufficiently high removal rate cannot be obtained in somecases. If the average particle diameter exceeds 1000 nm, inhibition ofdishing and erosion sometimes becomes insufficient, and a stable aqueousdispersion cannot be readily obtained in some cases because ofprecipitation or separation of the abrasive grains. Although the averageparticle diameter of the abrasive grains may be in the above range, itis in the range of more preferably 10 to 700 nm, particularly preferably15 to 500 nm. If the average particle diameter is in this range, astable chemical mechanical polishing aqueous dispersion having a highremoval rate, capable of sufficiently inhibiting dishing and erosion andrarely suffering precipitation or separation of the abrasive grains canbe obtained.

[0042] If metal ions, such as iron, nickel and zinc, remain in asemiconductor device having been subjected to chemical mechanicalpolishing treatment, yield loss is frequently brought about. Therefore,even if these metal ions are contained in the abrasive grains, theamount of the metal ions is desirably in the range of usually not morethan −10 ppm, preferably not more than 5 ppm, more preferably not morethan 3 ppm, particularly preferably not more than 1 ppm. As a matter ofcourse, it is preferable that the abrasive grains do not contain thesemetal ions.

[0043] The abrasive grains are contained in an amount of preferably 0.01to 5% by weight, more preferably 0.02 to 4% by weight, based on thetotal amount of the chemical mechanical polishing aqueous dispersion(A). If the amount of the abrasive grains is less than 0.01% by weight,a satisfactory removal rate cannot be obtained in some cases. If theamount thereof exceeds 5% by weight, cost is increased, and besidesstability of the aqueous dispersion (A) sometimes becomes insufficient.

[0044] (Organic Compound having Heterocyclic Ring)

[0045] The organic compound having a heterocyclic ring for use in theaqueous dispersion (A) is, for example, an organic compound having atleast one heterocyclic ring selected from the group consisting offive-membered heterocyclic rings and six-membered heterocyclic ringshaving at least one nitrogen atom. Examples of the heterocyclic ringsinclude five-membered heterocyclic rings, such as pyrrole structure,imidazole structure and triazole structure; and six-memberedheterocyclic rings, such as pyridine structure, pyrimidine structure,pyridazine structure and pyrazine structure. These heterocyclic ringsmay form condensed rings. Examples of the condensed rings include indolestructure, isoindole structure, benzimidazole structure, benzotriazolestructure, quinoline structure, isoquinoline structure, quinazolinestructure, cinnoline structure, phthalazine structure, quinoxalinestructure and acridine structure.

[0046] Of the organic compounds having such structures, preferable areorganic compounds having pyridine structure, quinoline structure,benzimidazole structure or benzotriazole structure. As the organiccompounds, quinolinic acid, quinaldinic acid, benzimidazole andbenzotriazole are preferable, and quinolinic acid and quinaldinic acidare more preferable.

[0047] The organic compound having a heterocyclic ring is contained inan amount of preferably 0.01 to 5% by weight based on the total amountof the chemical mechanical polishing aqueous dispersion (A). If theamount of the organic compound having a heterocyclic ring is less than0.01% by weight, a satisfactory removal rate cannot be obtained in somecases. When the organic compound having a heterocyclic ring is containedin an amount of 5% by weight, a sufficient effect is obtained.Therefore, in consideration of the economical efficiency, it isunnecessary to add the organic compound having a heterocyclic ring in anamount of more than 5% by weight.

[0048] (Surface Active Agent)

[0049] The surface active agent for use in the aqueous dispersion (A)is, for example, a cationic surface active agent, an anionic surfaceactive agent or a nonionic surface active agent.

[0050] Examples of the cationic surface active agents include aliphaticamine salts and aliphatic ammonium salts. Examples of the anionicsurface active agents include fatty acid soap; carboxylates, such asalkyl ether carboxylates; sulfonates, such as alkylbenzenesulfonate,alkylnaphthalenesulfonate and α-olefin sulfonate; sulfates, such ashigher alcohol sulfate and alkyl ether sulfate; and phosphates, such asalkylphosphate.

[0051] Examples of the nonionic surface active agents include ether typesurface active agents, such as polyoxyethylene alkyl ether; ether-estertype surface active agents, such as polyoxyethylene ether of glycerolester; ester type surface active agents, such as polyethylene glycolfatty acid ester, glycerol ester and sorbitan ester; acetylene glycol;ethylene oxide addition product of acetylene glycol; and acetylenealcohol.

[0052] The surface active agent is contained in an amount of preferablynot more than 2% by weight, more preferably 0.01 to 2% by weight, basedon the total amount of the chemical mechanical polishing aqueousdispersion (A). If the amount of the surface active agent is less than0.01% by weight, dishing, erosion and the like cannot be sufficientlyinhibited in some cases. If the amount of the surface active agentexceeds 2% by weight, decreasing of a removal rate is induced, andbesides, foaming cannot be inhibited in some cases.

[0053] (Oxidizing Agent)

[0054] Examples of the oxidizing agents for use in the aqueousdispersion (A) include hydrogen peroxide; organic peroxides, such asperacetic acid, perbenzoic acid and tert-butyl hydroperoxide;permanganic acid compounds, such as potassium permanganate; bichromicacid compounds, such as potassium bichromate; halogenic acid compounds,such as potassium iodate; nitric acid compounds, such as nitric acid andiron nitrate; perhalogenic acid compounds, such as perchloric acid;persulfates, such as ammonium persulfate; and heteropolyacid. By theaddition of these oxidizing agents, a removal rate can be more greatlyimproved.

[0055] Of the above oxidizing agents, hydrogen peroxide, organicperoxides and persulfates such as ammonium persulfate are particularlypreferable because their decomposition products are harmless.

[0056] The oxidizing agent is contained in an amount of preferably 0.01to 9% by weight, more preferably 0.02 to 6% by weight, particularlypreferably 0.03 to 5% by weight, based on the total amount of thechemical mechanical polishing aqueous dispersion (A). If the amount ofthe oxidizing agent is less than 0.01% by weight, oxidation action ofcopper sometimes becomes insufficient, and a satisfactory removal ratecannot be obtained in some cases. When the oxidizing agent is containedin an amount of 9% by weight, a sufficient effect is obtained.Therefore, in consideration of the economical efficiency, it isunnecessary to add the oxidizing agent in an amount of more than 9% byweight.

[0057] (Other Additives)

[0058] The chemical mechanical polishing aqueous dispersion (A) canfurther contain various additives when needed, in addition to the abovecomponents. By the addition of various additives, dispersion stabilitycan be further enhanced, a removal rate can be increased, and when theaqueous dispersion (A) is used for polishing two or more films havingdifferent hardness, a difference in the removal rate between these filmscan be controlled.

[0059] More specifically, by the addition of an organic acid or aninorganic acid, an aqueous dispersion (A) having a higher removal ratecan be obtained. Examples of the organic acids includepara-toluenesulfonic acid, dodecylbenzenesulfonic acid, isoprenesulfonicacid, gluconic acid, lactic acid, citric acid, tartaric acid, malicacid, glycolic acid, malonic acid, formic acid, oxalic acid, succinicacid, fumaric acid, maleic acid and phthalic acid. Examples of theinorganic acids include nitric acid, sulfuric acid and phosphoric acid.These acids may be used singly or in combination of two or more kinds.Further, amino acids, such as glycine, alanine and glutamic acid; andwater-soluble polymers, such as urea, polyacrylamide, polyacrylic acid,polyvinyl pyrrolidone and hydroxyethyl cellulose are also employablewhen needed.

[0060] By adding an alkali to the aqueous dispersion (A) and therebyadjusting pH, a removal rate can be increased. In this case, it ispreferable to appropriately adjust pH in a range where the abrasivegrains are stably present by considering electrochemical properties of asurface to be polished, disperibility and stability of polymer particlesand a removal rate. Examples of alkalis employable herein includeorganic bases, such as ethylenediamine, ethanolamine andtetramethylammonium hydroxide; and inorganic bases, such as hydroxidesof alkali metals, specifically sodium hydroxide, potassium hydroxide,rubidium hydroxide and cesium hydroxide, and ammonia.

[0061] By appropriately selecting components of the chemical mechanicalpolishing aqueous dispersion (A) and if necessary adjusting pH tocontrol a removal rate as described above, a chemical mechanicalpolishing aqueous dispersion (A) having desired polishing performancecan be obtained.

[0062] (B) Chemical Mechanical Polishing Aqueous Composition

[0063] The chemical mechanical polishing aqueous composition (B) is notspecifically restricted in its composition provided that it is achemical mechanical polishing aqueous composition containing at leastone organic compound having a heterocyclic ring. The chemical mechanicalpolishing aqueous composition (B) can contain abrasive grains, a surfaceactive agent and an oxidizing agent when needed, within limits notdetrimental to the object of the present invention. Similarly to thecase of the chemical mechanical polishing aqueous dispersion (A), byappropriately selecting components of the chemical mechanical polishingaqueous composition (B) and if necessary adjusting pH to control aremoval rate, a chemical mechanical polishing aqueous composition (B)having desired polishing performance can be obtained.

[0064] (Organic Compound having Heterocyclic Ring)

[0065] Examples of the organic compounds having a heterocyclic ring foruse in the aqueous composition (B) include the same compounds aspreviously exemplified for the aqueous dispersion (A). The organiccompound having a heterocyclic ring contained in the aqueous composition(B) may be the same as or different from the organic compound having aheterocyclic ring contained in the aqueous dispersion (A). The organiccompound having a heterocyclic ring is contained in an amount of usually0.005 to 3% by weight based on the total amount of the chemicalmechanical polishing aqueous composition (B). If the amount of theorganic compound having a heterocyclic ring is less than 0.005% byweight, increase of dishing and erosion and occurrence of corrosioncannot be inhibited in some cases. When the organic compound having aheterocyclic ring is contained in an amount of 3% by weight, asufficient effect is obtained. Therefore, in consideration of theeconomical efficiency, it is unnecessary to add the organic compoundhaving a heterocyclic ring in an amount of more than 3% by weight.

[0066] (Abrasive Grains)

[0067] Although the chemical mechanical polishing aqueous composition(B) preferably contains no abrasive grain, the aqueous composition (B)may contain abrasive grains in an amount not detrimental to the objectof the present invention. When the abrasive grains are contained, theabrasive grain concentration is preferably not more than ½ the abrasivegrain concentration of the aqueous dispersion (A). When the aqueouscomposition (B) contains no abrasive grain or contains abrasive grainsin the above-mentioned abrasive grain concentration, increase of dishingcan be inhibited and corrosion will not occur. Hence, yield loss can beprevented.

[0068] Examples of the abrasive grains for use in the aqueouscomposition (B) include the same abrasive grains as previouslyexemplified for the aqueous dispersion (A). The abrasive grainscontained in the aqueous composition (B) may be the same as or differentfrom the abrasive grains contained in the aqueous dispersion (A).

[0069] (Surface Active Agent)

[0070] Examples of the surface active agents for use in the aqueouscomposition (B) include the same surface active agents as previouslyexemplified for the aqueous dispersion (A). The surface active agentcontained in the aqueous composition (B) may be the same as or differentfrom the surface active agent contained in the aqueous dispersion (A).The surface active agent is contained in an amount of preferably 0.005to 1% by weight based on the total amount of the chemical mechanicalpolishing aqueous composition (B). When the amount of the surface activeagent is not less than 0.005% by weight, dishing, erosion and the likecan be sufficiently inhibited, but the amount thereof is preferably notmore than 1% by weight from the viewpoint that decreasing of a removalrate and foaming can be inhibited.

[0071] (Oxidizing Agent)

[0072] Although the chemical mechanical polishing aqueous composition(B) preferably contains no oxidizing agent, the aqueous composition (B)may contain an oxidizing agent in an amount not detrimental to theobject of the present invention. When the oxidizing agent is contained,the oxidizing agent concentration is preferably not more than ½ theoxidizing agent concentration of the aqueous dispersion (A). When theaqueous composition (B) contains no oxidizing agent or contains anoxidizing agent in the above-mentioned oxidizing agent concentration,increase of dishing can be inhibited and corrosion will not occur.Hence, yield loss can be prevented.

[0073] Examples of the oxidizing agents for use in the aqueouscomposition (B) include the same oxidizing agents as previouslyexemplified for the aqueous dispersion (A). The oxidizing agentcontained in the aqueous composition (B) may be the same as or differentfrom the oxidizing agent contained in the aqueous dispersion (A).

Chemical Mechanical Polishing Method

[0074] The chemical mechanical polishing method according to theinvention is a method for chemical mechanical polishing of a metal layerformed on a surface of a semiconductor substrate, on said surface ametal wiring portion being present, in the production of thesemiconductor substrate (FIG. 1(c) or 2(c)) comprising the substratehaving a trench and a metal material buried in the trench, said metalmaterial forming the metal wiring portion, which comprises polishing themetal layer with feeding the chemical mechanical polishing aqueousdispersion (A), and subsequently, polishing the metal layer remaining onthe non-wiring area during the above polishing with feeding the chemicalmechanical polishing aqueous composition (B) in addition to the chemicalmechanical polishing aqueous dispersion (A). A barrier metal layer maybe formed on the bottom and internal surface of the trench in thesubstrate and on the substrate surface in which the trench is present,when needed (FIG. 2).

[0075] The semiconductor substrate having a metal layer on such asurface is, for example, a semiconductor substrate which is obtained inthe production process of a semiconductor device such as super LSI andwhich has not been subjected to polishing treatment.

[0076] Examples of metals for forming the metal wiring portion and themetal layer include pure metals, such as pure tungsten, pure aluminumand pure copper; and alloys of tungsten, aluminum or copper and othermetals. The material to constitute the non-wiring portion is notspecifically restricted provided that it is a material having insulatingproperties, and is, for example, silicon oxide or an insulating resin.Examples of metals to constitute the barrier metal layer includetantalum, titanium, tantalum nitride and titanium nitride.

[0077] As a polishing apparatus, a commercially available chemicalmechanical polishing apparatus (e.g., EPO-112 model and EPO-222 modelmanufactured by Ebara Corpration, LGP-510 model and LGP-552 modelmanufactured by Lap Master SFT Co., Mirra (trade name) manufactured byApplied Materials Inc.) is employable.

[0078] The chemical mechanical polishing method according to theinvention is further described in more detail with reference to figures,but it should be construed that the invention is in no way limited tothe figures. A semiconductor substrate material to be polished is amaterial wherein a metal layer 4 is formed on the surface of asemiconductor substrate, where a metal wiring portion is present (FIG.1(a) or 2(a)). As shown in FIG. 1(a) or 2(a), the semiconductorsubstrate comprises a substrate 2 having a trench and a metal material 1buried in the trench. The metal material forms a metal wiring portion.

[0079] First, such a semiconductor substrate as shown in FIG. 1(a) or2(a) is set in a polishing apparatus, and the metal layer 4 is polishedwith feeding the chemical mechanical polishing aqueous dispersion (A).This polishing is conducted until the time (end point (FIG. 1(b) or2(b)) at which a layer different from the metal layer 4 is exposed in anon-wiring area 2 a other than the metal portion 1. The layer differentfrom the metal layer 4 is the substrate 2 a or the barrier metal layer 3b. This end point can be determined by measuring a value of a currentthat flows into a motor during the polishing and thereby detecting achange of torque or by detecting an eddy current by an eddy currentmethod or by optically detecting a change of color of the surface to bepolished.

[0080] The polishing conditions, such as type of polishing pad, carrierload, carrier rotating speed, table rotating speed and flow rate of theaqueous dispersion (A), are appropriately determined according to thematerial of the metal layer to be polished.

[0081] In the above polishing until the end point by the use of only thechemical mechanical polishing aqueous dispersion (A), the metal layerfrequently remains on the non-wiring portion (FIG. 1(b) or 2(b)).Therefore, subsequently to the polishing until the end point,over-polishing is carried out for a predetermined time with feeding thechemical mechanical polishing aqueous composition (B) in addition to thechemical mechanical polishing aqueous dispersion (A) to remove theremaining metal layer 4 a. The over-polishing time is appropriatelydetermined on an experimental basis, and is preferably 0 to 50% of thepolishing time until the end point. The polishing conditions, such astype of polishing pad, carrier load, carrier rotating speed, tablerotating speed, flow rate of the aqueous dispersion (A) and flow rate ofthe aqueous composition (B), are appropriately determined according tothe material of the metal layer to be polished. The flow rate of theaqueous dispersion (A) during the over-polishing is preferably not morethan that during the polishing until the end point. The flow rate of theaqueous composition (B) is preferably 0.5 to 2 times the flow rate ofthe aqueous dispersion (A).

[0082] After the metal layer are polished as described above, abrasivegrains remaining on the surface of the semiconductor substrate arepreferably removed by, for example, a usual cleaning method.

[0083] As described above, polishing is carried out with feeding onlythe aqueous dispersion (A) until the substrate or the barrier metallayer is exposed, and then over-polishing is carried out with feedingthe aqueous composition (B) in addition to the aqueous dispersion (A),whereby increase of dishing can be prevented, and polishing free fromcopper remaining can be attained. According to the chemical mechanicalpolishing method of the invention, further, flat and excellent metalsemiconductor substrate can be obtained without occurrence of corrosion.Further according to the chemical mechanical polishing method of theinvention, after the polishing until the end point by the use of onlythe aqueous dispersion (A), the aqueous composition (B) is just added,whereby polishing can be readily conducted and the above metalsemiconductor substrate is obtained.

[0084] If polishing is carried out until the end point by the use ofonly the aqueous dispersion (A) and over-polishing is subsequentlycarried out for a predetermined time by the use of only the aqueousdispersion (A) in order to remove a remaining metal layer 4 a, the metalwiring portion is polished during over-polishing, and hence dishingbecomes large. Further, if the over-polishing time is shortened toinhibit increase of dishing, the remaining metal layer 4 a cannot besufficiently removed. Furthermore, if both of the polishing until theendpoint and the over-polishing are carried out with feeding only theaqueous composition (B), a removal rate is extremely low, and hence ametal semiconductor substrate cannot be readily produced.

EXAMPLES

[0085] The present invention is further described with reference to thefollowing examples, but it should be construed that the invention is inno way limited to those examples. The terms “part(s)” and “%” used inthe examples and the comparative examples mean “part(s) by weight” and“% by weight”, respectively, unless otherwise noted.

Preparation Example 1

[0086] (Preparation of Fumed Silica Particle-Containing AqueousDispersion)

[0087] 100 Parts by weight of fumed silica particles (available fromNippon Aerosil Co., Ltd., trade name: AEROSIL #90) were dispersed in 900parts by weight of ion-exchanged water by means of an ultrasonicdispersing machine, and the resulting dispersion was filtered through afilter having a pore size of 5 μm to prepare an aqueous dispersion (1)containing 10% by weight of fumed silica particles.

Preparation Example 2

[0088] (Preparation of Colloidal Silica-Containing Aqueous Dispersion)

[0089] In a 2-liter flask, 70 parts by weight of ammonia water having aconcentration of 25% by weight, 40 parts by weight of ion-exchangedwater, 175 parts by weight of ethanol and 21 parts by weight oftetraethoxysilane were poured, and they were heated to 60° C. withstirring at 180 rpm. At this temperature, stirring was continued for 2hours, and then cooling was achieved to obtain an alcohol dispersioncontaining colloidal silica having an average particle diameter of 97nm. Then, from the dispersion, an alcohol was removed by means of anevaporator with adding ion-exchanged water at 80° C. This operation wasrepeated several times to sufficiently remove an alcohol from thedispersion. Thus, an aqueous dispersion (2) containing 10% by weight ofcolloidal silica having an average particle diameter of 97 nm wasprepared.

Preparation Example 3

[0090] (Preparation of Aqueous Dispersion Containing Abrasive GrainsComprising Composite Particles)

[0091] In a 2-liter flask, 90 parts by weight of methyl methacrylate, 2parts by weight of methoxypolyethyleneglycol methacrylate (availablefrom Shin-nakamura Chemical Co., Ltd., trade name: NK ester M-90G #400)5 parts by weight of 4-vinylpyridine, 2 parts by weight of an azo typepolymerization initiator (available from Wako Pure Chemical Industries,Ltd., trade name: V50) and 400 parts by weight of ion-exchanged waterwere placed, and they were heated to 70° C. with stirring in a nitrogengas atmosphere. At this temperature, polymerization was performed for 6hours to obtain an aqueous dispersion containing polymethyl methacrylateparticles having an average particle diameter of 150 nm, wherein theparticles have a functional group having a cation of an amino group anda polyethylene glycol chain. The polymerization yield was 95%. In a2-liter flask, 100 parts by weight of this aqueous dispersion containing10% by weight of polymethyl methacrylate particles were poured, and 1part by weight of methyltrimethoxysilane was added, followed by stirringat 40° C. for 2 hours. Thereafter, 50 parts by weight of aqueousdispersion containing 10% by weight of colloidal silica (available fromNissan Chemical Industries, Ltd., trade name: Snowtex 0) was stepwiseadded over a period of 2 hours to mix them. The mixture was furtherstirred for 2 hours to give an aqueous dispersion containing particleswherein silica particles had adhered onto the polymethyl methacrylateparticles. Then, to the aqueous dispersion, 2 parts by weight ofvinyltriethoxysilane were added, and they were stirred for 1 hour.Thereafter, 1 part by weight of tetraethoxysilane was further added, andthe dispersion was heated to 60° C., followed by stirring for 3 hours.Then, the dispersion was cooled to give an aqueous dispersion (3)containing 10% by weight of composite particles. The composite particleshad an average particle diameter of 180 nm and were particles whereinsilica particles had adhered onto 80% of surfaces of the polymethylmethacrylate particles.

Examples 1 to 6

[0092] (1) Preparation of Chemical Mechanical Polishing AqueousDispersion (A)

[0093] In a 10-liter polyethylene container, a given amount ofion-exchanged water was placed, and to the water, a compound having aheterocyclic ring and a surface active agent shown in Table 1 were addedso as to give concentrations shown in Table 1, followed by sufficientstirring. With stirring of the.mixture, an oxidizing agent shown inTable 1 was added so as to give an oxidizing agent concentration shownin Table 1. Then, the aqueous dispersion obtained in the abovepreparation example was added so as to give an abrasive grainconcentration shown in Table 1, followed by sufficient stirring.Thereafter, the resulting dispersion was filtered through a filterhaving a pore size of 5 μm to give a chemical mechanical polishingaqueous dispersion (A).

[0094] (2) Preparation of Chemical Mechanical Polishing AqueousComposition (B)

[0095] In a manner similar to that in the preparation (1) of thechemical mechanical polishing aqueous dispersion (A), components shownin Table 1 were added to ion-exchanged water so as to obtainconcentrations shown in Table 1. Thus, a chemical mechanical polishingaqueous composition (B) was obtained.

[0096] (3) Polishing of Wafer having Copper Wiring Pattern

[0097] A commercially available wafer having a copper wiring pattern(SEMATECH #831, metal wiring portion and metal layer: Cu, non-wiringportion: SiO₂, barrier metal layer: Ta) was set on a polishing apparatus(Ebara Corporation, model: EPO112), and the wafer was polished under thefollowing conditions with feeding the chemical mechanical polishingaqueous dispersion (A) at a flow rate shown in Table 2. An end point wasregarded as the time at which the copper layer on the non-wiring regionof the wafer was removed, namely, the time at which the barrier metallayer on the non-wiring area was exposed, and the end point wasdetermined by detecting a change of a table current value (change oftorque).

[0098] (Polishing Conditions)

[0099] Polishing pad: available from Rodel Inc. (U.S.A.), trade name:IC1000-050-(603)-(P)-S400J

[0100] Carrier load: 200 g/cm²

[0101] Carrier rotating speed: 80 rpm

[0102] Table rotating speed: 100 rpm

[0103] Subsequently to the above polishing until the end point, thewafer was over-polished (subsequent polishing) under the same polishingconditions as described above with feeding the chemical mechanicalpolishing aqueous composition (B) in addition to the chemical mechanicalpolishing aqueous dispersion (A) at flow rates shown in Table 2. Theover-polishing time was regarded as 20% of the polishing the time untilthe end point.

[0104] (4) Evaluation of Dishing

[0105] With regard to the 100 μm wiring portion of the wafer having beensubjected to the polishing (3), a distance (difference in height)between the plane formed by the insulating film or the barrier metallayer and the lowest point of the wiring portion was measured by the useof an accurate difference meter HRP (manufactured by KLA Tencor Co.) toevaluate dishing. The results are set forth in Table 2.

[0106] (5) Evaluation of Copper Remaining

[0107] The 0.35 μm wiring portion of the wafer having been subjected tothe polishing (3) was all observed by a light microscope to examinepresence of copper remaining. The results are set forth in Table 2.

[0108] (6) Evaluation of Corrosion

[0109] With regard to the 0.35 μm wiring portion of the wafer havingbeen subjected to the polishing (3), an edge portion of the copperwiring was observed by a scanning electron microscope to examinepresence of corrosion. The results are set forth in Table 2.

Comparative Example 1

[0110] Using the chemical mechanical polishing aqueous dispersion (A)used in Example 1, the wafer was polished to the end point in the samemanner as in Example 1. Then, the wafer was over-polished in the samemanner as in Example 1, except that only the chemical mechanicalpolishing aqueous dispersion (A) was fed at a flow rate shown in Table3. The resulting wafer was evaluated in the same manner as in Example 1.The results are set forth in Table 3.

Comparative Example 2

[0111] (1) Preparation of Chemical Mechanical Polishing AqueousComposition (b)

[0112] In a 10-liter polyethylene container, a given amount ofion-exchanged water was placed, and with stirring of the water, hydrogenperoxide was added so as to give a concentration shown in Table 1. Then,the aqueous dispersion (2) obtained in the aforesaid preparation examplewas added so as to give an abrasive grain concentration of 0.01%,followed by sufficient stirring. Thereafter, the resulting dispersionwas filtered through a filter having a pore size of 5 μm to give achemical mechanical polishing aqueous composition (b).

[0113] (2) Polishing of Wafer having Copper Wiring Pattern

[0114] Using the chemical mechanical polishing aqueous dispersion (A)used in Example 1, the wafer was polished to the end point in the samemanner as in Example 1. Then, the wafer was over-polished in the samemanner as in Example 1, except that the chemical mechanical polishingaqueous composition (b) were fed in addition to the chemical mechanicalpolishing aqueous dispersion (A) at flow rates shown in Table 3. Theresulting wafer was evaluated in the same manner as in Example 1. Theresults are set forth in Table 3.

Comparative Example 3

[0115] Using the chemical mechanical polishing aqueous dispersion (A)used in Example 1, the wafer was polished to the end point in the samemanner as in Example 1. The resulting wafer was evaluated in the samemanner as in Example 1. The results are set forth in Table 3. TABLE 1Ex. 1 Ex. 2 Ex. 3 Chemical mechanical polishing aqueous dispersion (A)Abrasive Particle aqueous aqueous aqueous grains dispersion dispersiondispersion dispersion (1) (1) (2) Type fumed fumed colloidal silicasilica silica Conc. (%) 1 2 2 Heterocyclic Type quinaldinic quinaldinicquinolinic compound acid acid acid Conc. (%) 0.2 0.2 1 Surface TypeDBS-K DBS-A SLA active agent Conc. (%) 0.1 0.1 0.1 Oxidizing Typehydrogen hydrogen hydrogen agent peroxide peroxide peroxide Conc. (%) 11 1 Chemical mechanical polishing aqueous composition (B) AbrasiveParticle none none aqueous grains dispersion dispersion (2) Type — —colloidal silica Conc. (%) — — 0.01 Heterocyclic Type quinaldinicquinolinic quinolinic compound acid acid acid Conc. (%) 0.1 0.1 0.2Surface Type nonion (1) nonion (2) nonion (3) active agent Conc. (%)0.05 0.01 0.02 Oxidizing Type none none hydrogen agent peroxide Conc.(%) — — 0.01 Ex. 4 Ex. 5 Ex. 6 Chemical mechanical polishing aqueousdispersion (A) Abrasive Particle aqueous aqueous aqueous grainsdispersion dispersion dispersion dispersion (3) (1) (2) Type compositefumed silica colloidal particles silica Conc. (%) 3 2 2 HeterocyclicType quinolinic quinaldinic quinolinic compound acid acid acid Conc. (%)0.2 0.2 1 Surface Type DBS-A DBS-A SLA active agent Conc. (%) 0.3 0.10.1 Oxidizing Type ammonium hydrogen hydrogen agent persulfate peroxideperoxide Conc. (%) 1 1 1 Chemical mechanical polishing aqueouscomposition (B) Abrasive Particle none none none grains dispersion Type— — — Conc. (%) — — — Heterocyclic Type quinaldinic quinaldinicquinolinic compound acid acid acid Conc. (%) 0.2 1.5 0.2 Surface Typenonion (4) none nonion (1) active agent Conc. (%) 0.05 — 1.5 OxidizingType none none hydrogen agent peroxide Conc. (%) — — 0.01

[0116] TABLE 2 Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 6 Polishing until Flowrate of aqueous dispersion (A) 200 150 300 250 150 300 end point(mL/min) Polishing time (sec) 185 125 175 108 125 175 Over-polishingFlow rate of aqueous dispersion (A) 200 150 300 250 150 300 (mL/min)Flow rate of aqueous composition (B) 200 200 300 400 200 150 (mL/min)Over-olishing time (sec)  37  25  35  22 25  35 Wafer evaluation 100 μmdishing (Å) 800 940 960 680 1200 850 Cu remaining none none none nonenone none (Light microscope observation) Corrosion none none none nonenone none (SEM observation)

[0117] TABLE 3 Comp. Ex. 1 Comp. Ex. 2 Comp. Ex. 3 Chemical mechanicalpolishing aqueous dispersion (A) Abrasive Particle aqueous aqueousaqueous grains dispersion dispersion dispersion dispersion (1) (1) (1)Type fumed fumed fumed silica silica silica Conc. (%) 1 1 1 HeterocyclicType quinaldinic quinaldinic quinaldinic compound acid acid acid Conc.(%) 0.2 0.2 0.2 Surface Type DBS-K DBS-K DBS-K active agent Conc. (%)0.1 0.1 0.1 Oxidizing Type hydrogen hydrogen hydrogen agent peroxideperoxide peroxide Conc. (%) 1 1 1 Chemical mechanical polishing aqueouscomposition (b) Abrasive Particle aqueous grains dispersion dispersion(2) Type colloidal silica Conc. (%) 0.01 Heterocyclic Type none compoundConcentration — (%) Surface Type none active agent Conc. (%) — OxidizingType hydrogen agent peroxide Conc. (%) 0.01 Comp. Comp. Comp. Ex. 1 Ex.2 Ex. 3 Polishing until Flow rate of aqueous 200 200 200 end pointdispersion (A) (mL/min) Polishing time (sec) 185 185 185 Over-polishingFlow rate of aqueous 200 200 — dispersion (A) (mL/min) Flow rate ofaqueous 0 300 — composition (b) (mL/min) Polishing time (sec) 37 37 —Wafer 100 μm dishing (Å) 2300 1750 650 evaluation Cu remaining none nonepresent (Light microscope observation) Corrosion present present none(SEM observation)

[0118] As can be seen from the results in Table 1 and Table 2, when thechemical mechanical polishing aqueous composition (B) were used inaddition to the chemical mechanical polishing aqueous dispersion (A)during the over-polishing, dishing was small, copper remaining andcorrosion did not take place, and good results were exhibited.Generally, dishing of not more than 1500 Å is preferable, and a waferhaving dishing of more-than 1500 Å is often judged as fail.

[0119] On the other hand, it can be seen that when the wafer waspolished by the use of only the chemical mechanical polishing aqueousdispersion (A) without using the chemical mechanical polishing aqueouscomposition (B) during the over-polishing, dishing was large andcorrosion took place (Comparative Example 1).

[0120] Further, it can be seen that when the wafer was polished by theuse of the chemical mechanical polishing aqueous composition (b)containing no heterocyclic compound instead of the chemical mechanicalpolishing aqueous composition (B) containing a heterocyclic compoundduring the over-polishing, dishing and corrosion both took place(Comparative Example 2).

[0121] Furthermore, it can be seen that when the over-polishing was notcarried out, copper remaining took place though dishing was good(Comparative Example 3).

[0122] In FIG. 3, a relationship between a ratio of the over-polishingtime to the polishing time until the end point and dishing is shown. Itcan be seen from FIG. 3 that increase of dishing during theover-polishing was inhibited by the use of the chemical mechanicalpolishing aqueous composition (B).

INDUSTRIAL APPLICABILITY

[0123] The chemical mechanical polishing agent kit of the presentinvention is useful for the production of semiconductor devices. In moredetail, the chemical mechanical polishing agent kit can be favorablyused in the process for forming wiring of a semiconductor devicerequiring mixed mounting of extremely fine wiring of about 0.05 μm towide wiring of about 100 μm, such as high-speed logic LSI, morespecifically, in a polishing step of the process.

[0124] According to the chemical mechanical polishing method of thepresent invention, increase of dishing and occurrence of corrosion canbe prevented, and a semiconductor device requiring mixed mounting ofextremely fine wiring of about 0.05 μm to wide wiring of about 100 μm,such as high-speed logic LSI, can be produced.

What is claimed is:
 1. A chemical mechanical polishing agent kitcomprising a combination of a chemical mechanical polishing aqueousdispersion (A) containing abrasive grains and a chemical mechanicalpolishing aqueous composition (B) which contains at least one organiccompound having a heterocyclic ring, wherein the aqueous composition (B)does not mix with the aqueous dispersion (A).
 2. The chemical mechanicalpolishing agent kit as claimed in claim 1, wherein the chemicalmechanical polishing aqueous composition (B) further contains a surfaceactive agent.
 3. The chemical mechanical polishing agent kit as claimedin claim 1, wherein: (i) the chemical mechanical polishing aqueouscomposition (B) contains no abrasive grain or contains abrasive grainsin a concentration of not more than ½ the abrasive grain concentrationof the chemical mechanical polishing aqueous dispersion (A), and (ii)the chemical mechanical polishing aqueous composition (B) contains theorganic compound having a heterocyclic ring in a concentration of 0.005to 3% by weight.
 4. The chemical mechanical polishing agent kit asclaimed in claim 3, wherein the chemical mechanical polishing aqueouscomposition (B) further contains a surface active agent in aconcentration of 0.005 to 1% by weight.
 5. The chemical mechanicalpolishing agent kit as claimed in claim 3, wherein the chemicalmechanical polishing aqueous dispersion (A) further contains anoxidizing agent, and the chemical mechanical polishing aqueouscomposition (B) contains no oxidizing agent or contains an oxidizingagent in a concentration of not more than ½ the oxidizing agentconcentration of the chemical mechanical polishing aqueous dispersion(A).
 6. The chemical mechanical polishing agent kit as claimed in anyone of claim 1, wherein the chemical mechanical polishing aqueousdispersion (A) contains the abrasive grains in a concentration of 0.01to 5% by weight, an organic compound having a heterocyclic ring in aconcentration of 0.01 to 5% by weight, a surface active agent in aconcentration of 0.01 to 2% by weight and an oxidizing agent in aconcentration of 0.01 to 9% by weight.
 7. A method for chemicalmechanical polishing of a metal layer formed on a surface of asemiconductor substrate, on said surface a metal wiring portion beingpresent, in the production of the semiconductor substrate comprising thesubstrate having a trench and a metal material buried in the trench,said metal material forming the metal wiring portion, which comprises:polishing the metal layer with feeding a chemical mechanical polishingaqueous dispersion (A) containing abrasive grains until a layerdifferent from the metal layer is exposed in a non-wiring area otherthan the metal portion, and subsequently, polishing the metal layerremaining on the non-wiring area during the above polishing with feedinga chemical mechanical polishing aqueous composition (B) containing atleast one organic compound having a heterocyclic ring in addition to thechemical mechanical polishing aqueous dispersion (A).